1. Field of the Invention
The present invention relates to a color display apparatus and, more particularly, to an adapter device for separating a sync signal from a sync-on-green video signal and a color display apparatus including the adapter device.
2. Description of the Related Art
Generally, a computer system uses red (R), green (G), and blue (B) video signals and horizontal and vertical synchronizing signals to display images on a display monitor. Modes of synchronizing video signals in recent computer systems are classified into a separate horizontal/vertical sync mode, a composite sync mode, and a sync-on-green (SOG) mode. In the separate sync mode, horizontal and vertical sync signals are separately transmitted from each other. In the composite sync mode, horizontal and vertical sync signals are compounded into a composite signal and then the composite signal is transmitted. And, in the SOG mode, a composite sync signal and a green (G) video signal are compounded and transmitted. Almost all of the recently developed computer display monitors support either the separate sync mode or the composite sync mode, but the SOG mode is still utilized in a few fields because it is efficient to long-distance transmission of a video signal and a share system that is shared with many display monitors. As a transmission technique has been developed, transmission characteristics are considerably improved. However, as personal computers widely spread out, demand of the SOG signal mode is rapidly reduced.
Most high-priced LCD monitors and CRT monitors basically employ the separate sync signal mode and the composite sync signal mode, and support the SOG signal mode in order to widen an application range thereof. In order to support the SOG signal mode, a sync signal separating circuit for separating a sync signal from an SOG signal must be embedded in such a monitor. Accordingly, price and power consumption of a monitor supporting the SOG signal mode is higher than those of a monitor not supporting it. In a power-save mode, a power-consumption difference therebetween is about hundreds of milliwatt (mW).
A computer having the SOG signal mode must employ a display monitor that supports the SOG signal mode. Therefore, a user must purchase a high-priced display monitor that can support the SOG signal mode. U.S. Pat. No. 5,229,853 to Robert L. Myers entitled System For converting A Video Signal From A First Format To A Second Format and U.S. Pat. No. 5,805,150 to Hironari Nishino et al. entitled Synchronous Signal Separation Circuit each discuss the use of a sync signal separation circuit to separate the sync signal from the green video signal and are incorporated-by-reference herein.
I have determined that by using a suitable adapter that enables a display monitor of the separate and composite sync signal modes to be used in a display apparatus of the SOG signal mode, the foregoing problems can be solved. That is, since high-priced display monitors supporting the SOG signal mode need not embed a sync signal separation circuit therein, manufacturing cost and power consumption can be reduced. Moreover, display monitors that do not support the SOG signal mode can be used with the computer having the SOG signal mode.
U.S. Pat. No. 5,767,820 to Bruce E. Bassett et al. entitled Head-Mounted Visual Display describes a control box capable of receiving sync-on-green video signals or video signals having separate sync signals to provide a video signal to a monitor and/or a head-mounted display.
The present invention is contrived to solve the foregoing problems. Therefore, it is an object of the invention to provide an adapter device that separates a sync signal from an SOG signal, and inputs the separated sync signal to a display monitor together with a video signal.
To achieve the above object of the invention, there is provided an adapter device including a first connector for inputting a red signal, a blue signal, and a sync-on-green (SOG) signal; a sync signal separating circuit for separating a sync signal from the SOG signal; and a second connector for outputting the red signal, the blue signal, the SOG signal, and the separated sync signal.
The first connector is composed of a plurality of BNC (Bayonet Neill-Concelman) connectors for inputting the red signal, the blue signal, and the SOG signal, respectively. And the second connector is composed of a D sub-connector or a 13W3 connector. The adapter device further includes a power input terminal for receiving an operation power of the sync signal separating circuit. The sync signal separating circuit outputs either a composite sync signal or separated horizontal and vertical sync signals.